Question: 30 Suppose we want to estimate the concentration (micogram/ml) of a specific dose of ampicillin in the urine after various periods of time. We recruit 25 volunteers who have received ampicillin and find they have a concentration of 7 micrograms/ml with a standard deviation of 2 micrograms/ml. Assume the underlying population distribution of concentrations is normally distributed (p. 197).

Find a 95% confidence interval for the population mean concentration.